The present disclosure relates to subject matter contained in Japanese Patent Application No. 11-319134 (filed on Nov. 10, 1999) and Japanese Patent Application No. 2000-50666 (filed on Feb. 28, 2000), which are expressly incorporated herein by reference in their entireties.
1. Field of the Invention
The present invention relates to a control wire driving mechanism for use in an endoscope to pull a control wire by rotation of a rotating member.
2. Description of the Prior Art
There has heretofore been known a control wire driving mechanism for use in a bending control device of an endoscope, for example. In the mechanism, a pinion (i.e. a toothed wheel) that is actuated to rotate with a control knob (or a control lever) is meshed with a rack connected to the proximal end of a control wire, and the rack is advanced or retracted linearly by rotating the pinion, thereby driving the control wire to advance or retract.
However, such a rack-and-pinion mechanism needs a space for travel of the rack on each of the front and rear sides of the pinion as viewed in the axial direction of the control wire. The necessary rack travel space is twice as long as the travel stroke of the control wire.
For this reason, the control knob cannot be disposed closer to the upper end of the control part. Consequently, it is impossible to ensure a sufficient length for the grip portion of the control part. This causes operability to be impaired.
In view of the above-described problem, one type of bending control device for an endoscope is arranged such that the proximal end portion of a control wire is wound on a pulley having a circumferential groove formed on the entire periphery thereof, and the control wire is pulled by rotation of the pulley. Such a pulley can be disposed closer to the upper end of the control part of the endoscope.
In such a mechanism, however, the end portion of the control wire must be secured to the pulley. Therefore, the maximum angle of rotation is limited considerably, and the control wire is likely to break owing to the stress concentration on the secured portion of the control wire.
Under these circumstances, a mechanism using a sprocket wheel as a rotating member has been put to practical use and widely used. In the mechanism, a chain connected to the proximal end of a control wire is meshed with the sprocket wheel to pull the control wire.
However, because the chain has a considerable thickness and height, the device becomes large and heavy when the chain is connected to the proximal end of the control wire, and hence the endoscope control part becomes unfavorably large and heavy. This gives rise to a problem because it is necessary for the operator to actuate the endoscope control part while holding it with his/her hand throughout the observation of the inside of a body cavity. In addition, the use of a chain causes the cost to rise unfavorably.
An object of the present invention is to provide a control wire driving mechanism for use in an endoscope in which a toothed wheel can be disposed at a position closer to the upper end of a control part of the endoscope, so that it is possible to ensure a sufficient length for the grip portion and hence possible to attain favorable operability, and which can be formed in an extremely simple, compact and lightweight structure at reduced cost and is also superior in function.
Other objects and advantages of the present invention will become apparent from the following detailed description of illustrated embodiments of the invention.
According to the present invention, there is provided a control wire driving mechanism for use in an endoscope. The control wire driving mechanism includes a toothed wheel actuated to rotate in a control part of the endoscope. A control wire has a cord-like member helically wound on and secured to the outer peripheral surface of a portion near the proximal end thereof at a pitch corresponding to the pitch of the toothed wheel. The control wire is meshed with the toothed wheel at the portion wound with the cord-like member.